1. Field of the Invention
The present invention relates to exercising equipment, specifically to barbells and dumbells, more specifically to those designed to be filled with a ballast, such as water, by the user, and those facilitating other types of exercises, such as situps, pushups, and aerobic stepping routines.
2. Description of the Prior Art
It has long been recognized that one of the most effective methods for enhancing physical fitness is through the use of free weights, such as barbells and dumbells. Interestingly, the names for these devices came about when early foundries, a large part of whose business was making bells, would turn out a cracked or otherwise unsatisfactory bell. With the clapper removed, such a bell was silent, or "dumb", yet still had great utility as a weightlifting device. Thus the one-handed free-weight came to be called a "dumbell." Obviously two such bells attached to a bar became a "barbell". The basic requirements of a barbell or dumbell are simple enough: a substantial mass, or ballast, which may be easily gripped by one or both hands in a balanced, comfortable way, with a shape facilitating weightlifting exercises. And in the past, the traditional central iron bar served admirably as a rigid frame for the barbell, contributing to the overall weight, and providing a long, convenient handle. Since even the very name "barbell" would not exist without the "bar", it may be hard for us to imagine the real article without its cylindrical namesake precursor. But in fact if we re-examine the above characteristics which a barbell must have, (a substantial mass, or ballast, which can be easily gripped by both hands in a balanced, comfortable way, with a shape facilitating weightlifting exercises) the word "bar" does not appear. And so the venerable bar is in fact not part of the invention which I will set forth here, although this invention will still occasionally be referred to as a "barbell".
It is a well-established fact that one of the cheapest, most convenient, and universally available sources of ballast is water. Over the years many attempts have been made to utilize the weight of water in a barbell. These attempts have largely utilized water filled weights attached to the traditional bar. (See U.S. Pat. No. 1,019,584 to Balston) With today's technology, the most economical, durable, versatile, and convenient way to contain and attach a handle to a volume of water happens to be with a plastic container. While plastics have certainly been incorporated into many modern barbells, it's usually the same old timeworn design, disk shaped weights on cylindrical iron bar. Normally the weights are a cast concrete disk, with a thin plastic shell providing merely a cosmetic exterior and a short-lived insurance against complete disintegration when the concrete cracks. Even when molded plastic water-fillable containers were introduced as weights, they were still attached to the ubiquitous iron bar. (See U.S. Pat. No. 4,199,140 to Ferretti.)
This is understandable since barbells have been around for such a long time, basically a relic of the iron age, and a mature technology with its reliance on a central cylindrical iron bar was in place long before the era of modem plastics. Barbells have achieved a certain traditional status, becoming in fact, an icon for the whole idea of weightlifting. The very maturity of this technology, however, is now what is holding it back; When an old technology works well enough, little need is seen for change. But times have changed, and materials have changed, and the new materials have different physical properties than the old, requiring new approaches to the design and engineering of products. Would you go out and buy a gallon of milk in a glass bottle, when a lighter, safer, easier to carry plastic alternative is available? How about a metal gasoline can, when a plastic one that won't rust, or bang around in your trunk is on the shelf next to it? Even the permanent gas tank on your car is probably plastic, because it's strong, durable, and economical.
Surely if plastics are such a versatile and durable material for containing and carrying liquids, and water is such a universally available source of ballast, a way to combine the two in the design of a modem barbell can be found. There are several methods of molding plastic into the shape of a closable container, including vacuum forming, injection molding, blow molding, and rotational molding. For our purposes, producing a large one-piece plastic container with a narrow threaded neck, the latter two show the most promise:
Rotational molding would offer the greatest design freedom. Using this process, virtually any shape or size of hollow plastic container can be formed, as long as the mold can be separated from the finished part. A threaded spout, or neck, can be easily formed into a part as long as it is exactly centered on the parting line, with its longitudinal axis perpendicular to the direction in which the two halves of the mold open and close. The finished parts are strong, thick walled, and durable. And the mold itself is not overly expensive to produce. If we could design the product, rotational molding could undoubtedly be used to produce a closable container, which when filled with water, would have a substantial mass, or ballast, easily gripped by one or both hands in a balanced, comfortable way, with a shape facilitating weightlifting exercises. But rotational molding is slow, requiring extended heating and cooling periods and large, cumbersome machinery to rotate many molds at a time. Why so many molds? Because each one can only turn out a few parts per day, due to the long cycle time. For these reasons rotational molding is used mainly to turn out short runs of large, heavy-duty products such as kayaks and children's swimming pools.
If we only needed a few hundred, or even a few thousand of this newly designed barbell, rotational molding might well be the way to go. But in this case we have to think bigger. The health and fitness movement has taken the world by storm, with just about everyone aware of the importance of exercise to good health. A truly revolutionary new product for the fitness market might easily sell into the millions of units. Of all the techniques for forming durable plastic containers in numbers of this magnitude, by far the most economical is blow molding. This is the technique whereby almost all modern plastic jugs and bottles are made. Even though the mold itself is very expensive, requiring special liquid-cooling channels, blow molding is fast, with a single mold able to turn out thousands of parts per day. It is well suited to our application, since a threaded spout, or neck can be handily formed into a blow-molded part. (provided that, as with rotational molding, such a threaded spout is exactly centered on the parting line, with its longitudinal axis perpendicular to the direction in which the two halves of the mold open and close.) If an ergonomic water-fillable barbell can be designed which can be efficiently produced by the technique of blow molding, it will be possible for almost anyone to personally own a complete set of barbells and dumbells having different weights, which in the past may have been cost-prohibitive. (Having a complete graduated set of freeweights is what commercial gyms and professional bodybuilders prefer; The convenience of being able to choose a barbell or dumbell of a given weight and begin using it immediately, without the delay of having to add or subtract plates, is important for continuity in a workout.) Blow molding offers economy of production, and great design freedom, but also has some constraints, which we will discuss, not found in other molding applications. Overcoming those constraints will turn a good idea into a great idea.
During the development of this invention, in concentrating upon the balance, ergonomics and manufacturability of a blow-moldable container for weightlifting, the concepts discovered and put forth herein actually offer an improved blow-moldable container in general:
1.) Typically, blow-molded containers with integrally molded handles have those handles located at the periphery of the structure as a whole, centered on the parting line, sometimes on top, or more usually to one side, near the top. In the latter case, when such a bottle is full and therefore at its heaviest, when held level in one hand, that hand, as well as the handle, must withstand gravitationally induced torsional stresses. Consider, for example, a typical gallon plastic milk jug, with its handle located to one side near the top. When held by the handle, such a jug will tend, due to gravity, to rotate to a position where its center of gravity is located below the handle. This tilted position is good for pouring. When pouring is not desired, however, such a container must be held upright, or the contents will spill. In order for the jug not to rotate to a position where its center of gravity is located below the handle, a torque must be applied to the container by the hand. The plastic comprising the handle and its surrounding regions must be thick enough to withstand this torque. Thicker material translates to higher manufacturing costs. From the user's point of view, counteracting this torque may result in a momentary inconvenience to most people, but may be painful or difficult for someone with, for example, arthritis. Often a second hand must be utilized to more easily carry such an unbalanced container. Our new design will locate the handle in the center of the container, where minimal gravitational torques will act upon it. In such a configuration, the container may be held upright or poured with equal ease, using only one hand. The addition of a flat area, or base, opposite the filling nozzle, would allow such a bottle to be stood upright without spillage when open.
Another example of prior art would be, for example, a blow-molded 5-gallon jug with the handle located on top. The combined center of gravity of the container and its contents is located directly below the handle, so the container is easy enough to carry with one hand. Pouring, however, requires two hands: one holding the handle and another to tip it from behind. Our improved design will allow both carrying and pouring with one-handed ease. With the handle located at the center of the container, the container may be easily rotated to any position whether empty, full or anywhere in between; if it is half-full, for instance, liquid contents will flow to lowest point whatever the orientation. In all orientations, this location of the contents will be approximately centered below the handle, since the handle is at the center, rather than the periphery, of the container.
2.) Blow-molded plastic containers in general are designed to have their walls as thin as possible, since when less material is used, the product is more economical to produce. While thin walls are desirable from an economic standpoint, a thin walled container may suffer from inadequate rigidity, and be unable to hold its shape, especially when filled with a hot liquid, as is often the case in bottling operations for foodstuffs. Many blow-molded bottles therefore incorporate strengthening ribs, webs, grooves, or other contours to enhance the stiffness of their walls. In our improved design, a central recess, or aperture, spanned by the handle, fully penetrates the container from one side to an opposing side. The walls of this central recess constitute a physical communication between the central regions of these two opposing sides of the container. This communication in turn prevents these sides from bulging outward from the pressure exerted by the contents. Since these two opposing sides will also have the largest surface area of any pair of opposing sides, this represents a real enhancement in strength, and will stabilize the shape of a container which might otherwise severely bulge when filled, especially with a hot liquid. The handle, spanning the central recess, further serves to unify the structure of the container.
Relatively soft and pliable plastics, such as HDPE (High Density Polyethylene) or polypropylene, are known for their impact resistance and tough durability, as well as for their ability to be blow-molded or rotationally molded. They are the types of materials normally utilized in milk bottles, fuel tanks, playground equipment for toddlers, jugs for orange juice or detergent, etc. While tough and resilient, neither their tensile strength nor their stiffness even approaches those of iron or steel. Our design should make efficient use of the limited strength offered by plastics of this type. In addition, all voids and recesses should be provided with sufficient draft angles, relative to the direction in which the mold opens and closes, to allow the finished part to be removed from the mold.
Summarizing so far, what is needed is a general design for a closable plastic container, which when filled with water, would have a substantial mass, or ballast, be easily gripped by one or both hands in a balanced, comfortable way, and have a shape facilitating weightlifting exercises. If the product can then be optimized for being produced by the technique of blow molding, that will facilitate economical mass production into the millions of units, and allow the average user to economically afford an entire set of barbells and/or dumbells having graduated weights. Once optimized for balance, ergonomics, and blow-moldability, the design will have certain advantages over existing blow-molded containers, as a container, beyond the scope of weightlifting.
Having developed a new type of barbell, as long as we are exercising anyway, let's look at what other exercises this new structure might also facilitate. What about abs? Curved tubular metal frames to guide and assist the motion of situps, the so-called "ab-roller" type of devices have proven extremely popular. In fact, since their recent introduction, literally billions of dollars worth of such devices to exercise the abdominal muscles have been sold. It seems that there is practically nobody who doesn't feel that their midriff could use a little work. Clearly, if we can find a way to make our product particularly useful for the performance of say, situps, we will have a much more useful and desirable product on our hands. And how about stair-stepping platforms? These simple elevated surfaces are now used in most aerobics classes because as simple as they are, they really work. Stepping aerobics are extremely popular, especially with women, who are often looking to maintain good tone, cardiovascular health, and slimness, rather than to "bulk up." So if our product could also function well in a capacity facilitating stepping aerobics, it would have great utility to that many more people, making it more likely that an entire family can enjoy it. And let's not forget the chest. Pushups are great for the chest muscles, as well as the lats, so if our product could somehow enhance the performance of pushups too, that would make it just about like having a complete gym in a bottle!
In U.S. Pat. No. 5,716,305 I do in fact show how to integrate situp, pushup, and stair-stepping functions into a fillable barbell designed to be produced from a two-piece mold. In the present manuscript I will disclose a new fillable design for both barbells and dumbells, further optimized specifically for being blow-molded. I will also teach how to integrate the situp, pushup, and stair-stepping functions of my previous design into a barbell of this new design.
There are other areas in the present invention where improvements have been made upon the concepts disclosed in this previous patent (U.S. Pat. No. 5,716,305). The first concerns further optimization of the design specifically for being produced by the process of blow-molding: In my earlier design, if a model had angled handles, the inner region of the recess, or apertures, containing each handle was also angled. The exterior of the unit in the regions surrounding the handles, on the other hand, may have been enlarged for clearance but was not necessarily angled similarly to the handles. In heavier and therefore thicker models such a difference in angle between the inner recesses and the exterior could result in certain areas having an undesirably high blow ratio (a term which will be explained soon). After much consideration a solution has been found which also enhances the ergonomics as well as the appearance of the product. This solution will be disclosed in the description of the new design for an improved barbell, optimized for blow-molding, as put forth herein.
Many of the general principles learned during the development of the two handed barbell have also been applied to a design for new type of one handed barbell, or dumbell, which will also be disclosed herein.
Another aspect of the previous design concerning the blow ratio as well as ergonomics and user comfort is that of the spacing of the handles and the foot insertion voids; In heavier, and therefore thicker models, for the foot insertion voids to be a comfortable distance apart, then for the regions separating these foot insertion voids from the handle recesses which straddle them to be wide enough in relation to their depth to have a proper blow ratio, the handles could end up being separated by more than we would really prefer for providing absolute best comfort to the most users. An elegant solution has been found, which will also be disclosed in this document.
One more area of improvement on my previous design concerns its function as a stair-stepping device for aerobics. An increased front-to-rear "footprint", or stance of the unit itself where it contacts the floor, to combat inadvertent rollover, including the use of auxiliary base members, as well as a detachable deck, for increased strength and traction, would enhance the utility of the device and will be disclosed herein.
Traditionally, an entire graduated set of freeweights requires either a lot of room or a rack for storage. Alternatively, an entire, graduated set of our affordable barbells and/or dumbells, each scaled (sized) so as to have a different weight when full, might advantageously be provided with contour means for fitably stacking together, for ease in packaging, shipping, and storage. Such stackability would also enhance the desirability of our product, especially the one handed (dumbell) version as a general means of packaging for pourable materials.
Notwithstanding the ease with which an entire graduated set of our new barbell might be manufactured, versions of our new, blow-moldable barbell wherein the weight can be selectively increased by the attachment of auxiliary weights, as with traditional barbells, may still be seen as desirable. If a way can be found to achieve this, within the constraints of the limited strength of our materials, and the fact that our product must be separable from a two-piece mold, it would be a notable improvement. Three related methods of achieving this selective weight-increasing feature will be disclosed herein.
Following is a discussion of the ideas revealed in some related patents:
U.S. Pat. No. 660,962, issued at the turn of the century to Kennedy shows an "Indian club" convertible to a "dumb bell" by the reverse insertion of a cylindrical threaded handle. This design is notable from the standpoint of the current invention as it exemplifies the maturity of the basic idea of a dumbell having a handle which spans a central recess.
U.S. Pat. No. 814,570 to Stockdell illustrates a grip for a dumbell, having an elongated, noncircular cross-section.
U.S. Pat. No. 1,019,584 to Balston discloses a rigid barbell or dumbell having fillable end sections threadably attached to a connecting bar. This early embodiment of the concept of a fillable barbell had utility limited to that of traditional barbells and dumbells, and was not useful for situps, leg lifts, pushups, or as a stepping type of device. The device had multiple sections including a separate, conventional bar and therefore could not be manufactured as a single unit. The conventional bar had inherently high shipping weight.
U.S. Pat. No. 1,366,200 to Matysek discloses fillable dumbells, attachable to a bar to constitute a barbell. This device is designed to be gripped by the hands only, and is not useful for situps, leg lifts, pushups, or as a stepping type of device. This device also had multiple sections including a separate, conventional bar and therefore could not be manufactured as a single unit. Here again, the conventional bar has an inherently high shipping weight.
U.S. Pat. No. 3,734,493 to Hasekian discloses a molded, one-piece dumbell incorporating an integral platform with restraining straps for the feet. While useful for both traditional dumbell exercises, and for situps and leg extensions, this device is not useful as a barbell, as a stepping type of device, or for pushups, and is not specified as fillable by the end user, so is expensive to manufacture and ship.
U.S. Design Pat. No. D244,628 issued Jun. 7, 1977 to Wright claims "The ornamental design for a dumbell as shown" with no mention of it being hollow or fillable, no ballast nor means for the introduction of such into the dumbell shown, described, or otherwise indicated. This design patent shows a dumbell matching the barbell of U.S. Design Pat. No. D244,629 issued the same day. Since these two design patents are so similar, to avoid redundancy the reader is asked to please apply the discussion of D244,629 below to this design patent as well.
U.S. Design Pat. No. D244,629 issued Jun. 7, 1977 to Wright shows a pair of apparently solid (with the exception of an axial bore to receive a bar) dumbells mounted on a bar. Since this patent claims "The ornamental design for a barbell, as shown", and does not show or describe the device as hollow, fillable with a ballast, or having a means for the introduction of such, I will not address it from that standpoint other than to say that it is so similar in appearance to the device in U.S. Pat. No. 4,029,312 issued to the same inventor exactly one week later, that the discussion of that patent which follows should suffice to describe any related issues which the reader may ascribe to this patent. Since the two patents even seem to share some artwork, I will mention that in a comparison of the multiple views shown in this one, the tall, thin regions which run alongside the handles (corresponding to those which Wright calls "peripheral side passages" in U.S. Pat. No. 4,029,312) measure out as being almost 4 times as tall as they are wide, making them non-blowmoldable if they were hollow.
U.S. Pat. No. 4,029,312 issued Jun. 14, 1977 to Wright discloses a pair of fillable dumbells which can be telescopically mounted on a rigid bar to constitute a barbell. Apertures located in the center of each dumbell provide access by either hands or feet without requiring attachments or alterations, providing convenient versatility. These dumbells are relatively lightweight when empty, and therefore this combination is less expensive to ship than conventional weights.
Disadvantages of this combination are that it incorporates a conventional bar, which does not lend itself to being formed by the same molding process as the dumbells, and that it is composed of three main parts, and so in any case cannot be molded as a single unit. The conventional straight bar has inherently high shipping weight. Also, the handles must be oriented coaxially with the bar, to telescopically receive the bar, while it is generally recognized that handles oriented at an angle to the longitudinal axis of a barbell are more comfortable for many exercises. In addition, the handles by default have a constant circular cross section, so they can telescopically receive the bar, while handles having a non-circular and/or non-constant cross-section have proven superior in many applications. The assembly has axial symmetry to the extent that it may roll away accidentally. The two sealable closure means, each consisting of a "material-receiving opening" and a "plug member", appear too small for easy filling without using a funnel, and in any case are quite archaic in nature, with the plug liable to accidentally fall out, or be pushed in, and get lost.
In fact, the whole concept of "a fillable barbell in which the weight can be varied by selectively increasing or decreasing the amount of ballast therein" being more convenient than the traditional approach where multiple weights can be selectively added or subtracted from a bar seems questionable: Where is the convenience, in the middle of a workout routine, of having to remove two plugs, then have a receptacle or faucet close at hand to provide a source for pourable ballast, and a sink, drain, or receptacle to dispose of unwanted ballast, in order to carefully measure and pour a specific amount into each dumbell, possibly needing a funnel, reseal them, then clean up any spillage which might have ensued? And what happens to the balance and usability of a dumbell or barbell which is, say, halfway full of a pourable, flowing ballast substance, free to slosh around inside, when such a device is tilted so that one side of each chamber is completely full and the other is completely empty? It seems that a better design, to fully take advantage of the cheaply abundant nature of water as a ballast, would be one where each barbell may be produced so inexpensively that a user could afford a whole set of them, each formed to have a different weight when full. To be able to fill each barbell through a single filling aperture, rather than two, would certainly be an additional convenience.
When reading about my present invention, one might be tempted to ascribe certain features of it to Wright's models, due to a similar "look". For example, the recesses, or apertures, which contain the handles in my invention fully penetrate the structure from one side to the other, with the handles spanning their narrowest middle regions, for reasons of moldability; By having our parting line follow the widest part of the handle and the narrowest section of the recess, and making the recesses flare outward in each direction from narrow middle region spanned by the handle, with proper draft angles for easy mold separation, we are providing a way for a two piece mold to close then open around the handle, and finally release the finished part. Wright on the other hand, is careful to specify (starting halfway down column 6 in U.S. Pat. No. 4,029,312) that "the central aperture 31 may be a recess rather than an opening all the way through the central portion of the weight 21." (Notice he is using the word "recess" differently from me.) He goes on to explain that having "an aperture entirely through the body of the shell is desired for symmetrical distribution of the mass." (not so it could provided with proper draft angles to be produced by a two-piece mold.) Note that if one of Wright's "central apertures" were "a recess rather than opening all the way through," as he states they could be, his barbell could definitely not be produced from a two-piece mold by thatfact alone. Referring to FIGS. 8 and 9 of this same U.S. Pat. No. 4,029,312, the walls of the "aperture" appear exactly parallel, with no attempt made to show any accommodation for draft angle requirements. An adequate draft angle would be especially important near such an interior parting line, as the cooling part will tend to shrink to it, rather than away from it. Since Wright never mentions specific molding processes, parting lines, draft angles, etc. we must consider his inventions, while somewhat similar in appearance to mine, as the far different sort of concept that they actually are.
While it may seem at first glance that the egg-shaped dumbells of this design could easily have been produced by blow-molding or rotational molding, actually, due to fact that the tubular "axial bore or channel" which telescopically receives the bar extends unbroken from one end of the generally spherical shell to the other, and the "central aperture" (which contains and is spanned by the handle) likewise fully penetrates the shell, but in a direction exactly perpendicular to the "axial bore or channel", it is geometrically impossible to produce a dumbell of this general type from a two-piece mold.
Additionally, if the long "axial bore or channel" is of constant diameter, which one would assume it is for it to "telescopically receive" a bar, then due to this feature alone it would be inseparable from a two-piece mold due to a lack of proper draft angles. While in his second claim, Wright makes reference to his "shell and said cylindrical element (handle) comprising a single unitary piece of molded plastic material", he in fact shows us a design which could not be cast in one piece by any conventional molding process. (In fact, this design was never actually manufactured, according to Wright, because of moldability problems having to do with the inclusion of this "axial bore or channel." It is worth noting that the one weightlifting product of Wright's design which was conmmercially developed, fillable dumbells sold under the name "Space-Weights", while not incorporating such an "axial bore or channel" were nevertheless produced by injection molding them in two halves, then gluing the halves together. None of Wright's designs was blow-molded, nor put forth as being blow-moldable.)
Further, if the design had been meant to be a fillable container produced from a two-piece mold, it could advantageously have incorporated a closable filling neck, as long as such a neck were centered on the parting line, with its longitudinal axis perpendicular to the direction in which the mold opens and closes. Such a neck could be shaped to accept a snap-on cap, but like the "plug means" cited in Wright's barbell, a snap-on cap must either be inconveniently small, or possibly be subject to accidental opening and/or loss, with this risk rising as the diameter of the cap or plug increases, since a larger closure will have a higher surface area-to-circumference ratio. More optimally, a closable container meant to be produced from a two piece mold can be provided with a threaded neck and a matching screw-on cap. A screw-on cap, regardless of size, is known to provide a tight, reclosable seal that is unlikely to accidently come off from a momentary or transient surge in ballast pressure the way a cork or snap-on cap might. Since Wright's material-receiving opening is located ninety degrees from any reasonable mold separation line, it is most certainly not designed to take advantage of the types of filling means made possible by two-piece molding techniques.
Another good reason that this design was not well suited for being produced by the technique of blow-molding, and certainly had not been optimized for it, has to do with the "blow-ratio": The cross section of this barbell taken at the handle shows that the narrow portions of the unit which run alongside the handles (which Wright calls "peripheral side passages") have a height-to-width ratio of about four. A common rule of thumb in the art of blow molding plastics is that unless absolutely necessary, the height-to-width ratio (called a blow ratio) of a finished part be no greater than about two. This is because the starting material, a hot extruded plastic tube (called a "parison"), has to stretch like a balloon when injected with pressurized air to fill each half of the mold, with its walls becoming thinner in the process. When any region of the mold has an unusually high blow ratio, (greater than about two) the entire parison must be made prohibitively thicker to compensate, resulting in undesirably high material usage, higher shipping weight, longer cooling times, and decreased production efficiency. These narrow portions in Wright's design could easily have been made wider if the inside surfaces facing the handles were simply aligned with the handles, rather than so severely arcing out away from them, which they do to allow the insertion of a user's foot. Because of this undesirably high blow ratio, we can infer that this fillable barbell was not meant to be blow-molded. (Note: Within the industry, there are two generally accepted definitions of the term "blow-ratio". One meaning refers to only half of the mold at a time, and is similar to the "draw" ratio of vacuum-forming. In that case the generally accepted maximum value is unity (1). Our use of the term in this document will always refer to the entire mold (both halves), or finished part, and so has a maximum value of two (2).)
To conclude then, the device of U.S. Pat. No. 4,029,312 to Wright is not a properly designed to be blow-molded, rotationally molded, or even produced as a single unit by any conventional molding process. The combination of its geometric non-moldability, a "material-receiving opening" obviously not located on a mold separation line, nor being provided with a threaded or snap-on neck and cap, as is a standard practice in the production of hollow molded plastic containers, as well as regions having an excessive blow-ratio make it obvious that Wright never seriously considered blow-molding or rotational molding as a means of production when designing this barbell. One underlying concept of Wright's design, to have a fillable barbell in which the weight can be selectively varied by adding or subtracting ballast, is fundamentally different from the concept which will be disclosed here, which is a design for a fillable barbell which, in sufficient numbers (to cover the rather steep initial tooling costs), is so inexpensive to manufacture that virtually anyone will be able to afford an entire graduated set of barbells, each having a different weight when completely full.
While noteworthy for its elegance and novelty, Wright's invention is not useful for pushups, and lacks utility as an aerobic stepping type of device. Larger filling apertures, to speed the filling process, and more positive closure means for such larger apertures, and/or reduction to a single aperture and closure, handles disposed at an angle and having a non-constant elliptical cross-section, as well as elimination of the conventional bar, discarding the unnecessary axial symmetry so it won't roll, and making the combination blow-moldable, would all be desirable improvements.
U.S. Design Pat. No. D267,737 Jan. 25, 1983 to Wright illustrates a smoothed barbell reminiscent of his earlier design (U.S. Pat. No. 4,029,312 Jun. 14, 1977, discussed above) for its reliance on the general form dictated by a central rigid cylindrical bar, onto each end of which two ovoid dumbells are telescopically fitted. Although this hollow barbell design appears as if it could possibly be fashioned as a one-piece unit, there is no means shown for a user to access the interior for adding ballast. Also, no ballast material is illustrated within the thick-walled, hollow shell. Since in this design patent, no "material-receiving opening" nor a "plug member" such as those which Wright shows in U.S. Pat. No. 4,029,312, nor any ballast material, are illustrated, described, or otherwise disclosed, we might conclude that this design patent does not show a barbell which is fillable by the user, but instead one which is meant to be used in its hollow state, as is, for example the exercise device in U.S. Pat. No. 4,673,179 to Pengler. (In Pengler's device, discussed below, a thick-walled empty structure with handles, while hollow, derives its mass not from any contained ballast, but from the density of its constituent materials, cited as "for example, a ceramic, a concrete aggregate, or other dense substance, even including metals such as aluminum and otherwise." The hollowness is actually to make it lighter, not heavier.) Further, if Wright's design were meant to be a fillable container produced from a two-piece mold, we might expect that it would advantageously incorporate a filling neck, possibly threaded, since the inclusion of such a neck is possible for blow-molded or rotationally molded containers for liquid, providing it can be located where it is centered on the parting line, with its longitudinal axis perpendicular to the direction in which the mold opens and closes.
Though this design patent illustrates an ornamental design for a "barbell" without the separate iron bar, the design itself still incorporates many vestigial features associated with a traditional barbell:
a.) The exterior shape of the unit as a whole has general rotational symmetry about a central longitudinal axis. This is a holdover from the time-worn concept of a cylindrical bar with attachable disk shaped weights. The design is unnecessarily constrained by this needless axial symmetry, as if it had been turned on a lathe, with such axial symmetry making the barbell prone to accidentally rolling. PA1 b.) The design incorporates a generally tubular midsection having a circular cross section. While a cross section of virtually any shape might be possible or desirable, Wright chose to follow the traditional form suggested by a central cylindrical bar here. PA1 c.) The handles are not only located on, but are coaxial with a central longitudinal axis. This is another carryover from the traditional concept of a barbell, where a single cylindrical bar served as both a structural frame for the assembled unit and as handle means. It is also reminiscent of Wright's earlier design, where two ovoid dumbells telescopically fit onto a traditional cylindrical bar. In that case, the handles slid over the bar, so the bar was constrained to be straight, and the handles were constrained to be coaxial with it. By eliminating a central bar, Wright had complete freedom to orient the handles at any angle, but did not explore that route. PA1 d.) The handles have a constant, circular cross-section, like a conventional bar, as opposed to an elliptical, and/or non-constant cross-section, as might be more desirable. PA1 1.) There is no ballast material shown or described. PA1 2.) There is no means shown or described for admitting any ballast material to the interior of the device, nor of sealably closing the device to prevent loss of ballast. PA1 3.) The weight in all embodiments is supplied by the mass of the structure itself, never by ballast: Toward the top of column 3 (U.S. Pat. No. 4,673,179) Pengler states, "Where weighted characteristics are required, the shell can comprise a metal, dense plastic, or other material." (The only embodiment of the device fillable with anything is mentioned in the next sentence, which continues, "Where weight is not desired, the shell can comprise a pair of spaced flexible plastic walls, the void therebetween being fillable with pressurized air.") Further down the same column, in describing his preferred embodiment, he specifies: "The material comprising the cube 10 can be, for example, a dense plastic, or can be a heavier material as, for example, a ceramic, a concrete aggregate, or other dense substances, even including metals, such as aluminum or otherwise." PA1 4.) Even in an embodiment of his invention which is "hollow" in the sense that the unit as a whole has an empty central region, as illustrated in his FIG. 4, Pengler states: "In this form of the device, the center 30 of the device is hollow, with the body of the cube being defined by a relatively thin shell 32. In order to provide sufficient weight in this form of the invention, the shell 32 preferably comprises a high density material, such as a metal, which can be cast or otherwise suitably formed to provide the indicated shape." We can assume that if Pengler had meant for his device to be fillable with ballast as a means of mass enhancement into this device, we would read about it at this point. To the contrary, Pengler describes the similarly centrally hollow embodiment illustrated in his FIG. 5 as "generally similar to the apparatus depicted in FIG. 4 except that structure has now been somewhat further simplified by the web portions 33 of FIG. 4 being eliminated so that the interior of the hollow device 50 is completely visible and accessible through the openings such as 52, 54 etc. into the shell interior 56." Obviously, such a hollow structure having a total of 24 holes on all sides, through which the interior is "completely visible and accessible", is not capable of containing a ballast material. PA1 5.) As mentioned, the one embodiment which is fillable, as Pengler shows in his FIG. 6, is fillable with air, not a ballast material. In this embodiment, each planar surface consists of a sandwich of compressed air between sheets of a flexible material, (like an air-mattress) while the handles remain solid. The walls, but not the main central generally hollow area, are inflatable, "through a suitable valve". So basically, Pengler's device is fillable with air, not a ballast, in an endeavor to make it lighter, not heavier. PA1 6.) In the only other embodiment of his device which makes use of two materials having different densities, as illustrated in Pengler's FIG. 3, a heavy solid core (metal is suggested) is buried within a lower density exterior (a relatively low density plastic is suggested), which includes the solid handles. PA1 a) not interfere with a user's body during the performance of the exercises for which this barbell device is designed. PA1 b) be capable of being the highest point in at least one orientation of the barbell, so that the unit can be completely filled with water by the force of gravity alone, leaving no air spaces or bubbles.
This design also is not optimized for being produced by the technique of blow molding. (According to Wright, the only weightlifting product of his design ever sold commercially, fillable dumbells called "Space-Weights", were produced by separately injection molding two halves, then gluing the two halves together to form one "Space-Weight".) The cross section of this barbell (FIG. 6, Des. 267,737 to Wright) taken at the handle shows that the narrow portions of the unit which run alongside the handles have a height-to-width ratio of about four. A common rule of thumb in the art of blow molding plastic is that unless absolutely necessary, the height-to-width ratio (called a blow-ratio) of a finished part be no greater than about two. This is because the starting material, a hot extruded plastic tube (called a "parison"), has to stretch like a balloon when injected with pressurized air to fill each half of the mold, with its walls becoming thinner in the process. When any region of the mold has an unusually high blow ratio, (greater than about two) the entire parison must be made thicker to compensate, resulting in undesirably high material usage, higher shipping weight, longer cooling times, and decreased production efficiency. These narrow portions in Wright's design, like those disclosed in U.S. Pat. No. 4,029,312, could easily have been made wider if the inside surfaces facing the handles were simply aligned with the handles, rather than so severely arcing out away from them, which they do to allow the insertion of a user's foot.
Because of this undesirably high blow ratio, and the lack of a spout or neck located on the mold separation line, as well as the fact that Wright does not mention blow-molding or, for that matter, even rotational molding or any other specific molding process in any of his barbell patents, we can assume that this design for a hollow barbell was not meant to be blow molded. Prototype molds for a similar device of Wright's are in fact injection molds, made of fiberglass, each intended to produce one half of the device. The two halves were to be glued together to form the final product.
Because the device illustrated lacks any apparent means for introducing or removing ballast, i.e. a hole, or for that matter, closure means, and does not in fact show any ballast present in the cross sectional views, we can infer that this is not a design for a fillable barbell. In fact, in the claim it is designated only as "The ornamental design for a barbell, as shown", with no mention of it being fillable.
U.S. Design Pat. No. D271,407 issued Nov. 12, 1983 to Wright claiming "The ornamental design for a dumbell, as shown" makes no reference, written, drawn, or otherwise inferred to it being hollow, molded, or fillable, with no opening or closure shown. Nonetheless, since it is yet another design of Wright's, let us address it from the standpoint of a blowmolder and point out that, from measurements of the illustrations shown, the discus-shaped members would have a blow ratio of 3.5:1, which is unacceptable, and made more so by the extremely sharp edges of their periphery.
U.S. Design Pat. No. D274,283 issued Jun. 12, 1984 to Wright again claiming only an ornamental design, not indicated as being hollow or fillable, nonetheless when measured and examined from a blow molding perspective, yields a blow ratio of three, effectively ruling out the process of blow-molding for the production of this otherwise simple and elegant design. Again, while this attractive device is clearly illustrated from all sides, the definite lack of any visible means for the introduction of ballast, the lack of any illustration or mention of any such ballast, or indeed any indication that this represents a hollow structure of any kind, would lead an unbiased reader to surmise that this ring-shaped hand-weight was to be fashioned of solid metal, plastic, a cementitious aggregate, or some combination of such conventional materials. Obviously, as claimed, the design is more ornamental than functional, since torques about the axis of the handle could be reduced by sacrificing the main circular shape, bringing the sections transverse to the handle closer to the handle. Such torques could also be more easily controlled if the handle were to have an elliptical, or other non-circular cross section. Also, judging the scale from the thickness of the handle, engagement with a user's hand could be improved by a more substantial flaring at the ends of the handle, and by allowing the ring to remain straight in the area where the handle attaches to it, so that a hand would not be "pinched" by the premature curve of the ring if the handle were gripped at one end. Certainly such increased flaring at the ends of the handle would enhance the strength of the interface between the handle and the ring. Of course if the structure were of solid iron, for instance, with the handle welded across the ring, we would expect a welding bead about the size of the minimal fillet shown at the seam between the two, and that abrupt transition would be O.K. because solid iron has ample material strength. If, on the other hand, the structure were meant to be a hollow molded plastic container, we would expect a much smoother transition (more pronounced flare) between the handle and the ring, so as to maximize the limited strength of the thin-walled, much softer material. A decision to try to blow-mold such a design would especially favor such increased flaring, and weigh against having the sharp corners illustrated, as such discontinuities can cause wrinkles and thin areas in the parison as it expands. To conclude, while there is no indication that this design was meant as a hollow, closable container, many serious factors, including an excessive blow-ratio and sharp edges, would militate against trying to produce a dumbell having an ornamental shape such as this by the technique of blow-molding.
U.S. Pat. No. 4,212,458 to Bizilia discloses one example of the many devices designed to anchor the feet of a user during the performance of situps, by attachment to the underside of a door. While useful for this designated purpose, it lacks utility for other types of exercises. This is an example of the proven desirability of being able to hold the feet down for the enhanced performance of situps.
U.S. Pat. No. 4,575,074 to Damratoski discloses a one piece molded fillable dumbell which may be used as either a hand or foot weight. This design for a lightweight dumbell is notable in that it seeks to minimize torque on the hand by having the contained ballast surround the hand instead of being concentrated at each end of a handle. Oddly, this device is restricted in its claims to having a handle which is off center. Damratoski goes into great detail regarding the exact measurements of his preferred embodiment, for example specifying that he has "found it preferable to make the handgrip 18 approximately 51/9 inch (13.34 cm.) long" (yes, you did read "approximately 51/9 inch"), further stating that he has "found that these dimensions will comfortably accommodate the hands of most users." One gets the feeling from reading this patent that he has gone to great lengths to try many shapes and sizes of handles, finally deciding on one with a rectangular cross section 3/4 inch wide by 11/8 inch deep. In any case we aren't given any information about what types of materials this invention is to be made from or how it is to be manufactured.
One thing is for sure, and that is that this dumbell could not be blow molded. Like Wright's models, discussed above, it exceeds our maximum permitted blow ratio of 2; Stating that he has "found that a weight of the type described herein will be suitable for use by the average person if the edge walls 26 and 28 are spaced 3 inches (7.62 cm.) apart," then going on to specify that "the distance from each flat segment of outer wall 22 to the corresponding segment of the inner wall 24 is 11/8 inch," Damratoski is giving us a prescription for disaster for anyone trying to blow mold such a shape. Taking a cross section of this hypothetical dumbell and dividing its depth of three inches by its width of 11/8 inch, we have a blow ratio of 2.667, which is way above what the industry is capable of. As previously discussed, a total depth to width, or "blow" ratio of about 2 is generally considered to be the maximum permissible in the art of blow-molding. Anyone doubting the veracity of such a rule would be advised to ask a blow molder, or better yet, try to find a blow-molded bottle or container, such as an oil, gasoline or juice container which has a blow ratio exceeding even one (1), that is, has its parting line on one of its longer sides. Not only that, but if you are going to try to "push the envelope" with respect to the blow ratio, you'll stand a much better chance if your shape has a rounded rather than a rectangular cross section. The square peripheries of these same "edge walls 26 and 28" in Damratoski's design definitely rule out such a miracle. (Picture yourself blowing bubble gum into a champagne glass versus a square box of the same size. In the case of the champagne glass, the bubble stretches evenly and contacts the whole surface of the interior at roughly the same time. In the case of the box, however, as the bubble advances toward the corners, it sticks to the sides of the box, becoming anchored there. The remaining region which is not yet stuck must become continually thinner as it advances toward the corner, unable to distribute the increased stretching over the bulk of the material which has become anchored to the walls of the box. Since the amount of material not "anchored" to the sides of the box is decreasing geometrically, while the area it must cover is also decreasing, but much less quickly, an actual breach of the material is quite likely before it ever actually reaches the corner.)
Like many fillable weightlifting devices, this one is designed so that the weight may be varied by the addition of different ballast materials, with Damratoski supplying us with a handy table showing how much it will weigh when filled with what. Although the configuration outlined might make a fine jogging weight, as the inventor notes, it is too light to be a serious weightlifting tool, even when filled with lead. In addition, the requirement that the handle be off-center to minimize any wasted clearance between the outside of the weight and the fingers, so as to minimize inertial torque on the hand, will actually cause a gravitational torque to be applied to the hand, possibly resulting in an unbalanced feel in a heavier, lead-filled unit. In conclusion, this jogging weight is not blow-moldable and lacks utility as a barbell or as an aerobic stepping type of device. It also does not aid in the execution of pushups.
U.S. Pat. No. 4,673,179 to Pengler discloses a polyhedron having handles formed by default at the filleted linear intersections of its component planar faces, by the excavation of a passage behind the middle of each such filleted linear intersection. Each such excavation continues the curve of the fillet a full 360 degrees to form a cylindrical handle, while allowing room for a hand to grasp it. This clever and attractive device is not to be confused with a moldable, ballast-fillable barbell for the following reasons:
a.) It's not a barbell: The device is described as consisting of a "geometrically regular body," meaning a regular polyhedron such as a cube, regular pyramid, etc. having only planar faces. The handles are located only at the exterior linear intersections of its component planar faces, instead of along a central, longitudinal axis. Such a shape is not conducive to most barbell-type exercises, due to interference with the user's body, as well as inconvenient orientation of the handles.
b.) It is not moldable: While Pengler is quite vague in describing how such a device would be manufactured, saying it is a "molded or otherwise formed one piece solid body, the shapes put forth in his patent, with their intricate latticework of holes, faces, hollows, and handles, could certainly not be produced from a two-piece mold. Just calling something "moldable" does not necessarily mean it is so.
c.) It is not ballast-fillable:
Since the denser core is a solid, permanent, built in component, this device makes no use of any introducible ballast, pourable or otherwise.
In conclusion, while this attractive exercise device has hollow areas, handles, and in one embodiment even has portions which can be inflated with compressed air, it is certainly not a moldable ballast-fillable barbell since, as described, it is neither moldable, ballast-fillable, nor even a barbell.
U.S. Pat. No. 4,679,788 to Adler discloses an exercise device having a weighted and padded cross arm on a post extending up from the base of the device. The base is designed for insertion under a bed mattress. Its primary use is to hold the feet of a user down during the performance of situps. It also has limited utility for leg exercises and as a relatively lightweight barbell. This device must be assembled from several distinct parts, and since its weight cannot be increased by the addition of ballast by the end user, is not particularly cheap to manufacture or ship.
U.S. Pat. No. 4,722,523 to Yang discloses a multiple use exercise kit which facilitates a wide variety of exercises. While quite versatile, this combination of many parts, including metal bars and weight plates, is heavy and expensive to produce and ship. It is also quite complicated to use, requiring reconfiguration between different types of exercise.
U.S. Pat. No. 4,773,640 to Kolbel et al. discloses a fillable dumbell, comprised of two weights and a coupling member, the coupling member surrounding a central ring diametrically spanned by a handle, which is free to rotate within the the ring, but supplied with adjustable frictional means to inhibit the rotation or stop it at any point. While Kolbel states that the fillable weights and coupling member may be blow-molded as a single unit, the handle and the ring which encircles it are separate units, which must be somehow attached to the blow-molded part. One is left wondering, if the two weights are formed by blow molding them as a single unit, what is the purpose of the very narrow (constricted) portion in the middle called a "web 5", and why is there a separate cap on each end, when a single blow molded container normally has continuous fluid communication throughout its interior? In his claim 3 Kolbel cites the coupling member as sealing the two chambers from one another, whereas in such a configuration, if blow molded, the coupling member would tend to connect, not separate the chambers, absent any reason for them to be pinched off from one another. If any part would seal the two halves, it would be the narrow web, which if blow-molded and shaped as shown, would still allow fluid communication between the two halves. An improvement would be to simply allow fluid communication between the two weights, reducing the required number of openings and caps from two to one, although in his claim 11, Kolbel does suggest (with no illustration to support it) that the dual screw-on caps could also be elongated to serve as handles.
Since, under ideal conditions, the process of blow molding allows any section of such a container to be twice as high as it is wide (a blow ratio of 2), this dumbell could be made more compact for a given weight if its length were reduced and its height increased. Further reduction in length could be achieved by making the coupling member and web both wider and thicker, making the weight distributed more evenly around the hand instead of confining it to two separate weights on each end. With such reduced length, the whole dumbell could be more easily rotated, possibly mitigating the dubious requirement for a rotating handle. If the handle did not have to rotate, it could be integrally molded with the weights, simplifying the design and reducing manufacturing costs. While this dumbell is designed on the premise that the weight may be varied by the addition of different ballast materials, in reality few persons would find constantly emptying and filling a single weight and storing the unused ballast easier than simply having a graduated variety of weights on hand. Also by the time you add the expense of the bearings and the screwed-together metal frame for the rotating metal handle, and then have to outlay further cash for a supply of differing ballast materials, what is the point of even having this model be fillable and blow molded, as opposed to just using a set of small iron dumbells which may obviously be rotated as needed?
Concluding, this patent is for a dumbell, but not a barbell, and due to its separate rotating handle and ring, could not be molded as a single unit.
U.S. Pat. No. 4,826,151 to Nuredin discloses an ankle-supporting stand for elevating the feet of a user, providing enhanced effectiveness in the performance of pushups. While well suited for its intended purpose, this device, by itself, does not facilitate a well-rounded exercise regimen.
U.S. Pat. No. 4,854,575 to Wilson et al. discloses a supposedly collapsible doughnut-shaped dumbell having accordion pleats around its periphery, with the idea that the weight of this dumbell can be slightly altered depending on how much ballast is used to fill it. Unfortunately, this appears to be yet another example of an idea which has not been fully thought through, for example:
1.) The accordion pleats are located exclusively on the outside walls of the dumbell, but not on the inside walls which define the void traversed by the handle. This means that only the outside walls could expand (get taller), but not the inside walls. This fact will severely limit the amount that the dumbell as a whole can expand, and is not discussed in this patent and indeed appears not to have even been considered in the design of this barbell.
2.) The top and bottom surfaces are shown as flat and level in both the full (FIGS. 3 and 5) and empty positions (FIG. 7), so we have a contradiction. It would be nice if the smooth inside walls could magically stretch (get taller) to match the stretching of the outer accordion-pleated wall, and so keep the top and bottom surfaces flat and level as shown, but in reality, only the outer accordion-pleated wall could expand. This limited expansion of just the outer wall would necessarily result in an inwardly or outwardly tilted top and bottom surface in either the closed or the open position. Take your pick, but the top and bottom surfaces couldn't both be level in both the open and closed positions if only the outside walls are expanding. This fact, while not mentioned in the patent, is apparent if one really thinks about it.
3.) FIG. 5 shows half of these exclusively outer accordion pleats being interrupted by the flat area which surrounds the inlet port, with no explanation of how this will affect the ability of the accordion pleats in this area to expand. A moment's reflection will reveal that the pleats will not function at the point where they connect to this flat area, further limiting in this region any limited expansion capability that this dumbell might have.
4.) In addition, this patent shows virtually no consideration of manufacturing techniques, or how this thing could actually be made. Our first clue is toward the end of the first paragraph in the Detailed Description, where Wilson states: "The location of the inlet port (20) and cap (22) is not critical. Advantageously the inlet is located on the outer periphery of the container (7) in the position illustrated in the various FIGS. 1, 2, 5 and 6 for convenience of introducing fluid, but other locations can be used if desired." Apparently Wilson has not considered how critical it might be that his inlet be located on a parting line, disposed with its longitudinal axis perpendicular to the direction in which the mold opens, for this product to even be made. Even FIG. 8, a detail view of the plug and inlet port does not show or mention a parting line.
5.) Such parting lines certainly needed to be considered, since Wilson vaguely states in the second paragraph of the Detailed Description that the pleats are molded biased into the closed position "by being molding using conventional techniques". Since the pleats run horizontally and form acute angles in the closed position (FIG. 7) a conventional two-piece mold would have to open horizontally to produce them. On the other hand, to form the void and handle, a two-piece mold would have to open vertically, as lines suggestive of parting lines within the central void and running along the handle in FIG. 1 would suggest. The squared edges at the ends of the accordion pleats, where they are interrupted by the flat area containing the inlet port would also require a vertically opening mold, but the pleats themselves would then prohibit separation of the part from the mold. Wilson shows signs of being aware of these drawbacks by the end of his Detailed Description, where he states: "The device (2), except for the screw-on cap (22) can be integrally molded in a single unit, or in two preferable symmetrical mirror image halves which are subsequently joined together, using a thermoplastic resin such as those exemplified above and using conventional molding techniques." Due to improper draft angles of the accordion pleats, this device could absolutely not be blow-molded from a conventional two-piece mold.
U.S. Pat. No. 4,750,630 to Campbell et al. discloses a generally elongated toroidal baby bottle, the two sides of which have narrowed central regions which function as handles for little hands. Due to the fact that it has a blow ratio of less than two, generously rounded comers, and its threaded filling neck is oriented with its longitudinal axis perpendicular to the direction in which a two-piece mold used to produce this shape would reasonably open, this well thought-out design could easily be blow molded. This popular example shows that useful, yet atypical handle designs for blow-moldable bottles have been considered and generally accepted in the past.
U.S. Pat. No. 4,867,325 to Dransfield discloses a toroidal baby bottle, having a bisecting tubular chamber which increases the capacity of the bottle. The two sides of the toroidal container act as handles, with the bisecting tubular chamber acting only to provide increased volumetric capacity and increased surface area for warming, but not as a handle itself. A flexible brush is included to reach throughout the interior. The opening for the attachment of a nipple is oriented at an angle of between "20 to 60 degrees with respect to the central plane of the bottle". Since this opening is shown with threads, such an angled orientation could inhibit separation of the part from the mold, if one were to attempt to produce this bottle from a two-piece mold by the technique of blow-molding. Also there are insufficient flares or fillets where the central tubular chamber meets the toroidal outer chamber, which could result in these sharply cornered areas having undue wall thinness, were one to attempt to produce this bottle by the technique of blow molding. This bottle is presented here because it is topologically similar to the thinnest embodiment of the dumbell of the present invention, but since it has two handles comprised by the outer toroid, while the middle tubular chamber is not a handle at all, but just a vessel, it is actually vastly different from the present invention.
U.S. Pat. No. 4,913,422 to Elmore et al. discloses a dumbell consisting of a handle with a sleeve at each end, into which fillable weights can be attached. Additional weights can then be attached to the first weights, etc.
U.S. Pat. Nos. 5,158,512 and 5,318,489 to Irwin et al disclose a stepping type of device for aerobic exercise. While elegant in its design and well suited to its purpose, it lacks utility for other types of exercise.
U.S. Pat. No. 5,393,284 to Wesley discloses a flexible, fillable barbell which may be reconfigured to become rigid by the insertion of a conventional bar. Straps for attachment to the feet are included. This device is portable and versatile, but must be reconfigured for different uses, and is not useful for pushups, situps, or as a stepping type of device. Also, the conventional bar has inherently high shipping weight.
U.S. Pat. No. 5,716,305 to this inventor discloses a molded hollow barbell having novel features facilitating a multiplicity of exercises, including voids for insertion of the feet from above and below, to facilitate the enhanced performance of situps, pushups, and leg extensions, as well functionality as a stair-stepping type of device.